Here's one such example:
http://www.spamcop.net/sc?id=z870315406z09...eff95a128316f8z
The content is invariably well written prose avoiding the rhetoric and hyperbole typical of much unsolicted advertising.
Since the messages avoid the SCBL and SpamAssassin isn't picking up the spam (at the level 2 I have selected) I can't think of what else can be done other than report when it arrives.
I'm certainly not keen for other spammers to start writing reasonable junk and flooding our mailboxes
Any ideas?
Andrew